<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>边框外轮廓</title>
  <style>
    div{
      width: 400px;
      height: 400px;
      border: 10px solid black;
      margin: 0 auto;
      background-color: gray;
      /* outline-style: solid;
      outline-width: 20px;
      outline-color: orange; */
      outline-offset: 10px;
      outline: 20px solid orange;
    }


  </style>
</head>
<body>
  <div ></div>
  
</body>
</html>